Electrical element package

ABSTRACT

Provided is an electrical element package, comprising an element substrate on which an electrical element is provided, a sealing substrate provided at a distance from a surface of the element substrate on a side of the electrical element so as to be opposed to the element substrate, and a glass frit for hermetically sealing a gap between the element substrate and the sealing substrate so as to surround the electrical element, wherein the electrical element package comprises a protective film for protecting an electrode from laser light applied in welding the glass frit, the protective film being provided between the element substrate and the glass frit.

TECHNICAL FIELD

The present invention relates to an electrical element package in which an electrical element such as an OLED, sensitive to an ambient environment, is hermetically sealed to prevent deterioration caused by oxygen, water, and the like in the ambient environment.

BACKGROUND ART

As is known, there have been made various research and development activities on an OLED display device (OLED display). In some fields such as a small-sized display device used for a cellar phone or the like, the OLED display device has already been put into practical use.

An OLED element (OLED layer) used for the OLED display device is a sensitive element which easily deteriorates when exposed to oxygen or water in an ambient environment. Therefore, for the practical use, the OLED layer is incorporated into the OLED display device in a state in which the layer is hermetically sealed so as to maintain display quality of the device and prolong a lifetime thereof.

An OLED element package in which an OLED layer is hermetically sealed generally has a structure in which a sealing substrate is provided at a distance from an element substrate on which the OLED layer is provided so as to be opposed to the element substrate, and a gap between the element substrate and the sealing substrate is hermetically sealed with a glass frit so as to surround the OLED layer provided on the element substrate. At this time, laser light is applied from the sealing substrate side to heat the glass frit so that the glass frit softens to be welded to the element substrate and the sealing substrate, to thereby form a hermetically sealed structure.

When the laser light is applied to the glass frit, however, an electrode (for example, an ITO electrode) for supplying electric power from the exterior to the OLED layer and the OLED layer may be damaged by irradiation heat of the laser light. The reason is as follows. Specifically, the electrode for supplying electric power from the exterior to the OLED layer is provided below the glass frit. Therefore, if no countermeasure against the irradiation heat of the laser light is taken, the electrode located below the glass frit is unduly heated by the irradiation heat of the laser light to be thermally damaged and, in some cases, disconnection may occur. Moreover, if the electrode is heated as described above, the heat may be transmitted through the electrode to the OLED layer to bring about a situation in which the OLED layer is thermally damaged.

Therefore, in general, when the OLED element package is manufactured, various countermeasures against heat, for preventing the irradiation heat of the laser light from being transmitted to the electrode or the OLED layer, are implemented.

For example, Patent Literatures 1 and 2 disclose that a laminate of a metal layer and an improvement layer for improving an adhesive force is provided on a substrate side on which an OLED element is provided, and a glass frit is welded to the improvement layer so as to join a substrate on which the OLED layer is provided, and a substrate opposed thereto. With this, even if laser light is applied in welding the glass frit, the laser light can be reflected by the metal layer. Therefore, the transmission of the irradiation heat of the laser light to the electrode connected to the OLED layer becomes hard. Thus, an effect of preventing the electrode and the OLED layer from being thermally damaged can be expected.

CITATION LIST

-   Patent Literature 1: JP 2010-80341 A -   Patent Literature 2: JP 2010-80339 A

SUMMARY OF INVENTION Technical Problem

In the case where the metal layer functioning as a reflective film for reflecting the laser light is used as disclosed in Patent Literatures 1 and 2, however, if the glass frit is directly welded to the metal layer, an adhesive force therebetween cannot be sufficiently maintained. Therefore, it is indispensably necessary to provide the improvement layer for improving the adhesive force between the metal layer and the glass frit. Moreover, when the metal layer is held in contact with the electrode connected to the OLED element, there arises a problem in that the metal layer and the electrode become conductive to each other. Therefore, it becomes also indispensably necessary to provide an insulating layer between the metal layer and the electrode. Therefore, a problem of a lowered degree of freedom in design of the OLED element package may arise.

It should be noted that, although the OLED element has been described above as an example, the same problem may arise even for an electrical element other than the OLED element when the electrical element is liable to be affected by an external environment and is hermetically sealed with the glass frit. Moreover, even in other fields such as a lighting device and a solar cell as well as the display device, the same problem may arise when the electrical element package is used.

In view of the current conditions described above, a technical object of the present invention is to reduce a situation in which an electrode or an electrical element is damaged by irradiation heat of laser light applied in welding a glass frit as much as possible while ensuring the degree of freedom in design of an electrical element package.

Solution to Problem

In order to achieve the technical object as above, the present invention provides an electrical element package, comprising, an element substrate on which an electrical element is provided, a sealing substrate provided at a distance from a surface of the element substrate on a side of the electrical element so as to be opposed to the element substrate, and a glass frit for hermetically sealing a gap between the element substrate and the sealing substrate so as to surround the electrical element, wherein the electrical element package comprises a protective film for protecting an electrode from laser light applied in welding the glass frit, the protective film being provided between the element substrate and the glass frit. The present invention includes, as specific embodiments thereof, a first aspect and a second aspect shown below.

The first aspect of the present invention is an electrical element package, comprising, an element substrate on which an electrical element is provided, a sealing substrate provided at a distance from a surface of the element substrate on a side of the electrical element so as to be opposed to the element substrate, a glass frit for hermetically sealing a gap between the element substrate and the sealing substrate so as to surround the electrical element, and a reflective film for reflecting laser light applied in welding the glass frit, the film being provided between the element substrate and the glass frit, wherein the reflective film is formed of a multilayer dielectric film obtained by alternately laminating a low-refractive index dielectric layer and a high-refractive index dielectric layer.

According to the configuration described above, the reflective film for reflecting the laser light applied in welding the glass frit is formed of the multilayer dielectric film obtained by alternately laminating the low-refractive index dielectric layer and the high-refractive index dielectric layer. The dielectric layers constituting the multilayer dielectric film have excellent adhesiveness to the glass frit. Therefore, even without additionally providing a bonding-force improvement layer only for increasing the adhesive force to the glass frit, in addition to the multilayer dielectric film, the adhesive force to the glass frit can be well maintained. Moreover, the dielectric layers constituting the multilayer dielectric film do not have conductivity. Therefore, even without additionally providing an insulating layer, electric insulation from the electrode connected to the electrical element can be maintained. Accordingly, additionally providing the bonding-force improvement layer for improving the adhesive force to the glass frit and the insulating layer is not an indispensable condition. As a result, the degree of freedom in the design of the electrical element package can be ensured.

Moreover, with the multilayer dielectric film as described above, a high reflectance can be easily realized in a wavelength band of the used laser light by selecting a material and adjusting a thickness for each of the low-refractive index dielectric layer and the high-refractive index dielectric layer. Therefore, when the laser light is applied to weld the frit glass, the laser light is reliably reflected at the multilayer dielectric film toward the frit glass so as to be effectively used to heat the frit glass. Therefore, the laser light transmitted through the multilayer dielectric film to be applied to the electrode or the like is reduced as much as possible. Accordingly, it becomes possible to reliably prevent a situation in which the electrode or the electrical element is unduly heated by the laser light to be thermally damaged.

In the above-mentioned configuration, the multilayer dielectric film may be welded directly to the glass frit, or the multilayer dielectric film may be formed directly on an electrode connected to the electrical element.

Specifically, as already described above, the multilayer dielectric film has a high adhesive force to the glass frit and insulation property, and therefore can be directly welded to the glass frit or directly formed on the electrode connected to the electrical element. With this, the configuration of the electrical element package is simplified to facilitate the manufacturing.

In the above-mentioned configuration, it is preferred that the low-refractive index dielectric layer have a refractive index of 1.6 or less, and the high-refractive index dielectric layer have a refractive index of 1.7 or more.

With this, a difference in refractive index between the low-refractive index dielectric layer and the high-refractive index dielectric layer can be appropriately kept so as to well maintain the reflectance to the laser light.

In the above-mentioned configuration, it is preferred that the multilayer dielectric film have a reflectance of 50% or more to the laser light.

With this, most part of the laser light applied in welding the glass frit can be reflected toward the glass frit. Therefore, it is possible to more reliably prevent a situation in which the electrode or the electrical element is damaged by the irradiation heat of the laser light.

In the above-mentioned configuration, the glass frit may contain 80 to 99.7 mass % of inorganic powder comprising SnO-containing glass powder and 0.3 to 20 mass % of a pigment. Herein, the term “SnO-containing glass powder” means glass powder containing, as a glass composition, 20 mol % or more of SnO. Moreover, the term “inorganic powder” means powder of an inorganic material other than (excepting) a pigment and generally means a mixture of glass powder and a refractory filler.

With this, the glass frit comprises the SnO-containing glass powder. Therefore, a softening point of the glass powder is lowered to lower a softening point of the whole glass frit. Then, when the inorganic powder comprising the SnO-containing glass powder is set within the above-mentioned range, the softening point of the glass frit is adequately lowered. Therefore, welding (sealing) with the laser light can be completed within a short period of time, whereas a welding strength thereof can also be increased. It should be noted that, if the content of the inorganic powder is less than 80 mass %, the glass frit does not soften and flow sufficiently when welding with laser light, and therefore, it becomes difficult to maintain a high welding strength.

Further, the glass frit contains 0.3 to 20 mass % of the pigment. When the content of the pigment is controlled to 0.3 mass % or more, the laser light becomes more likely to be absorbed by the glass frit. Therefore, the irradiation heat of the laser light can efficiently act on the glass frit. Thus, only a portion of the glass frit, which is to be welded, is more likely to be locally heated. As a result, the electrode and the electrical element can be prevented from being thermally damaged. On the other hand, when the content of the pigment is restricted to 20 mass % or less, a situation in which the glass frit devitrifies can be prevented when the glass frit is welded by the irradiation heat of the laser light.

In this case, the SnO-containing glass powder may contain, as a glass composition in terms of mol %, 35 to 70% of SnO and 10 to 30% of P₂O₅.

With this, the water resistance of the glass frit can be easily increased while a low-melting-point characteristic of the glass frit is maintained.

Next, the second aspect of the present invention is an electrical element package, comprising, an element substrate on which an electrical element is provided, a sealing substrate provided at a distance from a surface of the element substrate on a side of the electrical element so as to be opposed to the element substrate, and a glass frit for hermetically sealing a gap between the element substrate and the sealing substrate so as to surround the electrical element, wherein the electrical element package comprises a metal oxide film for protecting an electrode from laser light applied in welding the glass frit, the film being provided between the element substrate and the glass frit.

According to the configuration described above, the metal oxide film is formed between the element substrate and the glass frit. Therefore, when the laser light is applied to the glass frit to melt the glass frit, that is, at the time of laser welding, the contact between the glass frit and the electrode can be avoided as much as possible while the heat generated by the applied laser light is suppressed.

Further, according to the configuration described above, a high welding strength can be obtained even without additionally providing an improvement layer for increasing the adhesive force to the glass frit. Moreover, the metal oxide film does not have conductivity. Therefore, the electric insulation from the electrode connected to the electrical element can be maintained even without additionally providing the insulating layer. As a result, the degree of freedom in the design of the electrical element package is improved, which in turn leads to a reduction in the manufacturing cost of the electrical element package.

In the above-mentioned configuration, it is preferred that the metal oxide film have a thickness of 10 to 500 nm. With this, the electrode can be reliably protected while separation occurring between the glass frit and the metal oxide film after the laser welding is prevented.

In the above-mentioned configuration, it is preferred that the metal oxide film comprise any one of SiO₂, ZrO₂, Y₂O₃, TiO₂, Al₂O₃, Ta₂O₅, and Nb₂O₅. Such the metal oxide films have particularly excellent adhesiveness to the glass frit and insulating property.

In the above-mentioned configuration, it is preferred that the metal oxide film be welded directly to the glass frit, or formed directly on an electrode connected to the electrical element. With this, the configuration of the electrical element package can be simplified. Therefore, the manufacturing efficiency of the electrical element package is improved. As described above, the metal oxide film is excellent in adhesive force to the glass frit as well as in insulating property. Therefore, the metal oxide film can be directly welded to the glass frit, or the metal oxide film can be directly formed on the electrode connected to the electric element.

In the above-mentioned configuration, it is preferred that the glass frit contain 80 to 99.5 mass % of inorganic powder comprising SnO-containing glass powder and 0.05 to 20 mass % of a pigment. With this, the glass frit comprises the SnO-containing glass powder. Therefore, a softening point of the glass powder is lowered to lower a softening point of the glass frit. Then, when the inorganic powder comprising the SnO-containing glass powder is set within the above-mentioned range, the softening point of the glass frit is adequately lowered. Therefore, laser welding can be completed within a short period of time, whereas a welding strength thereof can also be increased.

In this case, it is preferred that the SnO-containing glass powder contain, as a glass composition in terms of mol %, 35 to 70% of SnO and 10 to 30% of P₂O₅. With this, the water resistance of the glass frit can be easily increased while a low-melting-point characteristic of the glass frit is maintained.

Advantageous Effects of Invention

As described above, according to the present invention, it is possible to reduce a situation in which the electrode or the electrical element is damaged by the irradiation heat of the laser light applied in welding the glass frit as much as possible while the degree of freedom in the design of the electrical element package is ensured.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A longitudinal sectional view illustrating a schematic configuration of an OLED element package according to an embodiment of the first aspect of the present invention.

FIG. 2 A sectional view taken along the line A-A in FIG. 1.

FIG. 3 A longitudinal sectional view illustrating a schematic configuration of an OLED element package according to an embodiment of the second aspect of the present invention.

FIG. 4 A sectional view taken along the line A-A in FIG. 3.

FIG. 5 A graph showing the results of simulation of frequency characteristics of reflectance of multilayer dielectric films.

FIG. 6 A graph showing the results of actual measurement of frequency characteristics of reflectance of multilayer dielectric films.

FIG. 7 A graph showing the results of actual measurement of temperature of electrodes at the time of laser welding.

FIG. 8 A graph showing the results of actual measurement of temperature of electrodes at the time of laser welding.

FIG. 9 A graph showing the results of actual measurement of temperature of glass frits at the time of laser welding.

FIG. 10 A schematic diagram illustrating a softening point of glass powder (SnO-containing glass powder) or a glass frit when measured with a macro-type DTA apparatus.

DESCRIPTION OF EMBODIMENTS

First, an embodiment of the first aspect of the present invention is described referring to the accompanying drawings. It should be noted that an OLED element package to be incorporated into an OLED display device is described below as an example of an electrical element package.

FIG. 1 is a longitudinal sectional view illustrating a schematic configuration of an OLED element package according to this embodiment. An OLED element package 1 comprises, as a basic configuration, an element substrate 3 on which an OLED layer 2 is formed, a sealing substrate 4 provided opposite to the element substrate 3 at a distance from a surface of the element substrate 3 on the OLED layer 2 side, and a glass frit 5 for surrounding the OLED layer 2 in a frame-like fashion so as to hermetically seal a gap between the element substrate 3 and the sealing substrate 4.

Each of the element substrate 3 and the sealing substrate 4 is formed of a glass substrate having a thickness of, for example, 0.05 to 0.7 mm in this embodiment.

A first electrode 6 and a second electrode 7, which are respectively connected to a back side and a front side of the OLED layer 2, are provided on the element substrate 3. The electrodes 6 and 7 pass below the glass frit 5 to be guided from the OLED layer 2 to the exterior of the package 1 so as to supply electric power to the OLED layer 2. It should be noted that the electrodes 6 and 7 branch according to a predetermined pattern, as illustrated in FIG. 2. The first electrode 6 on the back surface side of the OLED layer 2 is formed of, for example, a transparent electrode film (ITO film), whereas the second electrode 7 on the front surface side of the OLED layer is formed of, for example, a metal electrode film such as aluminum. It should be noted that the first electrode 6 and the second electrode 7 may both be formed of a transparent electrode film.

Then, as illustrated in FIGS. 1 and 2, laser light emitted from a laser L is applied from the sealing substrate 4 side to the glass frit 5 to heat the glass frit 5 so that the glass frit softens and flows to be welded to the element substrate 3 and the sealing substrate 4. With this, a hermetically-sealed structure of the package 1 is formed. As the laser L, for example, an infrared-ray laser (having a wavelength of 700 to 2500 nm) is used.

If the electrodes 6 and 7 are heated by irradiation heat of the laser light when the glass frit 5 is welded, there is a possibility of thermally damaging the electrodes 6 and 7. Moreover, there is another possibility of transmitting the heat through the electrodes 6 and 7 to the OLED layer 2 to thermally damage the OLED layer 2. Therefore, in this embodiment, a multilayer dielectric film 8 functioning as a reflective film is provided between the glass frit 5 and each of the electrodes 6 and 7 so as to reflect the laser light to the glass frit 5 side corresponding to the side opposite to the electrodes 6 and 7.

The multilayer dielectric film 8 is formed by alternately laminating a low-refractive index dielectric layer and a high-refractive index dielectric layer, and is set to have a reflectance of 50% or more (preferably 90% or more) in a wavelength band of the used laser light (for example, at 808 nm).

Specifically, the low-refractive index dielectric layer is made of a material having a refractive index of 1.6 or less, preferably a refractive index of 1.33 to 1.6. Examples of such material include silica (SiO₂), alumina (Al₂O₃), lanthanum fluoride (LaF₃), magnesium fluoride (MgF₂), and sodium aluminum hexafluoride (Na₃AlF₆). When the refractive index and thickness of the low-refractive index dielectric layer is defined as n1 and d1, respectively, and a wavelength of the laser light is defined as λ, an optical thickness (n1×d1) of the low-refractive index dielectric layer is set to λ/4.

The high-refractive index dielectric layer is made of a material having a refractive index of 1.7 or more, preferably a refractive index of 1.7 to 2.5. Examples of such material include a material obtained by adding small amount of titanium oxide (TiO₂), tin oxide (SnO), or cerium oxide (CeO₂), to titanium oxide (TiO₂), zirconium oxide (ZrO₂), tantalumpentoxide (Ta₂O₅), niobiumpentoxide (Nb₂O₅), lanthanum oxide (La₂O₃), silicon nitride (Si₃N₄), yttrium oxide (Y₂O₃), zinc oxide (ZnO), zinc sulfide (ZnS), or indium oxide (In₂O₃) as a main component. When the refractive index and thickness of the high-refractive index dielectric layer is defined as n2 and d2, respectively, and a wavelength of the laser light is defined as λ, an optical thickness (n2×d2) of the high-refractive index dielectric layer is set to an integral multiple of λ/4. It should be noted that, when the laser light having λ of 1200 nm or more, SiO₂ can also be used. When the laser light having λ of 1700 nm or more, GeO₂ can also be used.

It should be noted that, as the multilayer dielectric film 8, the number of laminated low-refractive index dielectric layers and high-refractive index dielectric layers is preferably four or more in total.

Further, it is preferred to provide different thermal expansion coefficients to the low-refractive index dielectric layer and the high-refractive index dielectric layer of the multilayer dielectric film 8. With this, as compared with the case where the refractive film for the laser light is formed to have a single layer, a stress due to thermal expansion at the time of welding with the laser light is significantly relieved. As a result, a crack is unlikely to be generated in the film. As a result, a situation in which oxygen or water enters from a portion of the multilayer dielectric film 8 can be reliably prevented. The reason is as follows. Specifically, when a multilayer film is formed on a substrate having a low thermal expansion coefficient such as glass, the multilayer film with high reliability can be formed with a laminated structure in which a layer having a compressive stress as an internal stress and a layer having a tensile stress as an internal stress are alternately laminated so that an internal stress of the whole multilayer film becomes small. In particular, an internal stress of the multilayer film formed on a substrate having a low thermal expansion coefficient (37×10⁻⁷/° C. or less) such as alkali-free glass exhibits the characteristics as described above. As a specific example, when SiO₂ which is a low-refractive index material and TiO₂ which is a high-refractive index material are laminated on an alkali-free glass substrate, the internal stress of the SiO₂ film is likely to become a compressive stress, whereas the internal stress of the TiO₂ film is likely to become a tensile stress. Therefore, the internal stresses of the SiO₂ film and the TiO₂ film are cancelled out. As a result, the internal stress becomes small as the whole multilayer film.

Here, a material for the glass frit 5, for example, there may be used a material comprising 80 to 99.7 mass % of inorganic powder comprising SnO-containing glass powder and 0.3 to 20 mass % of a pigment.

In this case, the content of the inorganic powder is preferably 90 to 99 mass %, more preferably 95 to 99 mass %, particularly preferably 97 to 99 mass %. If the content of the inorganic powder is small, the glass frit 5 does not soften and flow sufficiently at the time of welding, and it becomes difficult to enhance the welding strength at the time of the welding. On the other hand, if the content of the inorganic powder is more than 99.9 mass %, the content of the pigment becomes relatively small, and hence laser-light absorption performance of the glass frit 5 itself decreases. On the other hand, if the content of the pigment is too large, the thermal stability of glass is liable to deteriorate.

The average particle diameter D₅₀ of the SnO-containing glass powder is preferably less than 15 μm, more preferably 0.5 to 10 μm, particularly preferably 1 to 5 μm. When the average particle diameter D₅₀ of the SnO-containing glass powder is restricted to less than 15 μm, the gap between the element substrate 3 and the sealing substrate 4 can be easily narrowed. Accordingly, a time necessary for performing laser welding is shortened, and cracks and the like do not easily occur in a welding portion of the glass frit 5 even if there is a difference in thermal expansion coefficient between each of the element substrate 3 and the sealing substrate 4 and the glass frit 5. Herein, the term “average particle diameter D₅₀” refers to a value measured by laser diffractometry, and refers to a particle diameter at which the cumulative amount of particles starting from a particle having the smallest diameter reaches 50% in a cumulative particle size distribution curve on a volumetric basis in the measurement by laser diffractometry.

A maximum particle diameter D_(max) of the SnO-containing glass powder is preferably 30 μm or less, more preferably 20 μm or less, particularly preferably 10 μm or less. When the maximum particle diameter D_(max) of the SnO-containing glass powder is restricted to 30 μm or less, the gap between the element substrate 3 and the sealing substrate 4 can be easily narrowed, and cracks and the like do not easily occur in a welding portion of the glass frit 5, as in the above-mentioned case where the average particle diameter is restricted. Herein, the term “maximum particle diameter D_(max)” refers to a value measured by laser diffractometry, and refers to a particle diameter at which the cumulative amount of particles starting from a particle having the smallest diameter reaches 99% in a cumulative particle size distribution curve on a volumetric basis in the measurement by laser diffractometry.

The SnO-containing glass powder preferably contains 35 to 70% of SnO and 10 to 30% of P₂O₅ as a glass composition. The reasons why the glass composition is limited to such the range are described below. It should be noted that, in the description of the range of a glass composition, the expression “%” refers to “mol %” unless otherwise specified.

SnO is a component that contributes to lowering the melting point of glass. The content of SnO is preferably 35% or more, more preferably 35 to 70%, still more preferably 40 to 70%, most preferably 50 to 68%. Particularly when the content of SnO is 50% or more in glass, the glass easily softens and flows at the time of laser welding. If the content of SnO is less than 35% in glass, the viscosity of the glass becomes too high and it becomes difficult to perform laser welding with a desired laser output. On the other hand, if the content of SnO is more than 70% in glass, the vitrification of the glass is liable to be difficult.

P₂O₅ is a glass-forming oxide and is a component that enhances the thermal stability of glass. The content of P₂O₅ is preferably 10 to 30%, more preferably 15 to 27%, particularly preferably 15 to 25%. If the content of P₂O₅ is less than 10% in glass, the thermal stability of the glass is liable to deteriorate. On the other hand, if the content of P₂O₅ is more than 30% in glass, the weather resistance of the glass deteriorates, and hence it becomes difficult to ensure the long-term reliability of the OLED element package.

The following components can be added in addition to the above-mentioned components.

ZnO is an intermediate oxide and is a component that stabilizes glass. The content of ZnO is preferably 0 to 30%, more preferably 1 to 20%, particularly preferably 1 to 15%. If the content of ZnO is more than 30% in glass, the thermal stability of the glass may be liable to deteriorate.

B₂O₃ is a glass-forming oxide, is a component that stabilizes glass, and is a component that enhances the weather resistance of glass. The content of B₂O₃ is preferably 0 to 20%, more preferably 1 to 20%, particularly preferably 2 to 15%. If the content of B₂O₃ is more than 20% in glass, the viscosity of the glass may become too high and it may become difficult to perform laser welding with a desired laser output.

Al₂O₃ is an intermediate oxide and is a component that stabilizes glass. Further, Al₂O₃ is a component that lowers the thermal expansion coefficient of glass. The content of Al₂O₃ is preferably 0.1 to 10%, particularly preferably 0.5 to 5%. If the content of Al₂O₃ is more than 10% in glass powder, the softening point of the glass powder improperly may rise and it may become difficult to perform laser welding with a desired laser output.

SiO₂ is a glass-forming oxide and is a component that stabilizes glass. The content of SiO₂ is preferably 0 to 15%, particularly preferably 0 to 5%. If the content of SiO₂ is more than 15% in glass powder, the softening point of the glass powder may improperly rise and it may become difficult to perform laser welding with a desired laser output.

In₂O₃ is a component that enhances the thermal stability of glass and the content of In₂O₃ is preferably 0 to 5%. If the content of In₂O₃ is more than 5%, batch cost may rise.

Ta₂O₅ is a component that enhances the thermal stability of glass and the content of Ta₂O₅ is preferably 0 to 5%. If the content of Ta₂O₅ is more than 5% in glass powder, the softening point of the glass powder may improperly rise and it may become difficult to perform laser welding with a desired laser output.

La₂O₃ is a component that enhances the thermal stability of glass and is a component that enhances the weather resistance of glass. The content of La₂O₃ is preferably 0 to 15%, more preferably 0 to 10%, particularly preferably 0 to 5%. If the content of La₂O₃ is more than 15%, batch cost may rise.

MoO₃ is a component that enhances the thermal stability of glass and the content of MoO₃ is preferably 0 to 5%. If the content of MoO₃ is more than 5% in glass powder, the softening point of the glass powder may improperly rise and it may become difficult to perform laser welding with a desired laser output.

WO₃ is a component that enhances the thermal stability of glass and the content of WO₃ is preferably 0 to 5%. If the content of WO₃ is more than 5% in glass powder, the softening point of the glass powder may improperly rise and it may become difficult to perform laser welding with a desired laser output.

Li₂O is a component that contributes to lowering melting point of glass and the content of Li₂O is preferably 0 to 5%. If the content of Li₂O is more than 5% in glass, the thermal stability of the glass may be liable to deteriorate.

Na₂O is a component that contributes to lowering melting point of glass and the content of Na₂O is preferably 0 to 10%, particularly preferably 0 to 5%. If the content of Na₂O is more than 10% in glass, the thermal stability of the glass may be liable to deteriorate.

K₂O is a component that contributes to lowering melting point of glass and the content of K₂O is preferably 0 to 5%. If the content of K₂O is more than 5% in glass, the thermal stability of the glass may be liable to deteriorate.

MgO is a component that enhances the thermal stability of glass and the content of MgO is preferably 0 to 15%. If the content of MgO is more than 15% in glass powder, the softening point of the glass powder may improperly rise and it may become difficult to perform laser welding with a desired laser output.

BaO is a component that enhances the thermal stability of glass and the content of BaO is preferably 0 to 10%. If the content of BaO is more than 10% in glass, the balance of the components in the composition of the glass may be impaired, and the glass may be liable to denitrify to the worse.

F₂ is a component that contributes to lowering melting point of glass and the content of F₂ is preferably 0 to 5%. If the content of F₂ is more than 5% in glass, the thermal stability of the glass may be liable to deteriorate.

In view of providing thermal stability and low-melting-point characteristic, the total content of In₂O₃, Ta₂O₅, La₂O₃, MoO₃, WO₃, Li₂O, Na₂O, K₂O, MgO, BaO, and F₂ is preferably 10% or less.

In addition to the above-mentioned components, other components (such as CaO and SrO) can be added, for example, up to 10%.

It should be noted that, from the standpoint of reducing the batch cost of the SnO-containing glass powder, the content of transition metal oxides in the SnO-containing glass powder is preferably 10% or less, more preferably 5% or less, particularly preferably substantially zero. Herein, the phrase “substantially zero” refers to a case where the content of transition metal oxides in a glass composition is 3000 ppm (by mass) or less, preferably 1000 ppm (by mass) or less.

In addition, it is preferred that the SnO-containing glass powder be substantially free of PbO from an environmental standpoint. Herein, the phrase “substantially free of PbO” refers to a case where the content of PbO in the glass composition is 1000 ppm (by mass) or less.

On the other hand, it is preferred to use, as the pigment, an inorganic pigment, it is more preferred to use one kind or two or more kinds selected from carbon, Co₃O₄, CuO, Cr₂O₃, Fe₂O₃, MnO₂, SnO, and Ti_(n)O_(2n-1) (n represents an integer), and it is particularly preferred to use carbon. These pigments have excellent chromogenic property and absorb laser light well.

The pigment is preferably substantially free of Cr-based oxides from an environmental standpoint. Herein, the phrase “substantially free of Cr-based oxides” refers to a case where the content of Cr-based oxides in a pigment is 1000 ppm (by mass) or less.

The average particle diameter D₅₀ of the pigment is preferably 0.1 to 3 μm, particularly preferably 0.3 to 1 μm. Further, the maximum particle diameter D_(max) of the pigment is preferably 0.5 to 10 μm, particularly preferably 1 to 5 μm. If the particle size of the pigment is too large, the particles of the pigment may not easily disperse uniformly in the glass frit 5, and glass may not soften and flow locally at the time of laser welding. If the particle size of the pigment is too small, particles of the pigment easily aggregate to each other as well, and hence glass may also not soften and flow locally at the time of laser welding. The average particle diameter D₅₀ of primary particles of the pigment is preferably 1 to 5000 nm, 3 to 1000 nm, 5 to 500 nm, particularly preferably 10 to 100 nm. If the size of the primary particles of the pigment is too small, particles of the pigment easily aggregate to each other, and hence it may become difficult to disperse the pigment uniformly in the glass frit 5. Therefore, there is a possibility in that the glass frit 5 may not soften and flow locally at the time of laser sealing. On the other hand, if the size of the primary particles of the pigment is too large, it may become difficult to disperse the pigment uniformly in the glass frit 5 as well, and hence the glass frit 5 may not soften and flow locally at the time of laser sealing.

Further, the inorganic powder comprising the SnO-containing glass powder preferably comprises a refractory filler. With this, the thermal expansion coefficient of the glass frit 5 can be reduced and the mechanical strength of the glass frit 5 can be enhanced. The mixing ratio of the SnO-containing glass powder to the refractory filler in the inorganic powder is, in terms of vol %, preferably 40 to 100%:0 to 60%, particularly preferably 50 to 90%:10 to 50%. If the content of the refractory filler is more than 60 vol %, the ratio of the SnO-containing glass powder becomes relatively small and the efficiency of laser welding may be liable to deteriorate.

As the refractory filler, there may be used zircon, zirconia, tin oxide, quartz, β-spodumene, cordierite, mullite, quartz glass, β-eucryptite, β-quartz, zirconium phosphate, zirconium phosphate tungstate, zirconium tungstate, a compound having a basic structure of [AB₂ (MO₄)₃] such as NbZr(PO₄)₃, where A represents Li, Na, K, Mg, Ca, Sr, Ba, Zn, Cu, Ni, Mn, or the like, B represents Zr, Ti, Sn, Nb, Al, Sc, Y, or the like, and M represents P, Si, W, Mo, or the like, and a solid solution thereof.

The maximum particle diameter D_(max) of the refractory filler is preferably 30 μm or less, more preferably 20 μm or less, particularly preferably 10 μm or less. If the maximum particle diameter D_(max) of the refractory filler is more than 30 μm, some parts of welding portions of glass frit 5 are liable to have a thickness of 30 μm or more, and hence the gap between the element substrate 3 and the sealing substrate 4 may become non-uniform in the OLED element package 1, and consequently, it may become difficult to reduce the thickness of the OLED element package 1, that is the OLED display device. Further, when the maximum particle diameter D_(max) of the refractory filler is restricted to 30 μm or less, the gap between the element substrate 3 and the sealing substrate 4 can be easily narrowed. Accordingly, a time necessary for performing laser welding is shortened, and cracks and the like do not easily occur in a welding portion of the glass frit 5 even if there is a difference in thermal expansion coefficient between each of the element substrate 3 and the sealing substrate 4 and the glass frit 5.

The softening point of the glass frit 5 is preferably 450° C. or less, more preferably 420° C. or less, particularly preferably 400° C. or less. If the softening point of the glass frit 5 is more than 450° C., the efficiency of laser welding may be liable to deteriorate. The lower limit of the softening point of the glass frit 5 is not particularly limited, but in view of the thermal stability of glass, the softening point is preferably controlled to 300° C. or more. Herein, the term “softening point” refers to a value measured under a nitrogen atmosphere with a macro-type differential thermal analysis (DTA) apparatus, and in the DTA, the measurement starts from room temperature and the temperature increase rate is set to 10° C./min. It should be noted that the softening point measured with the macro-type DTA apparatus refers to a temperature (Ts) at a fourth inflection point illustrated in FIG. 10.

At present, an active matrix drive system, in which an active element such as a TFT is arranged at each pixel for driving, is adopted as a drive system in an OLED display. In this case, alkali-free glass (such as OA-10G manufactured by Nippon Electric Glass Co., Ltd.) is used for glass substrates for the OLED display. The thermal expansion coefficient of alkali-free glass is usually 40×10⁻⁷/° C. or less. On the other hand, the thermal expansion coefficient of a glass frit is 76 to 83×10⁻⁷/° C. in many cases. Thus, it was difficult to match the thermal expansion coefficient of a glass frit strictly to the thermal expansion coefficient of alkali-free glass. In contrast, the above-mentioned SnO-containing glass powder has good compatibility with a low-expansion refractory filler, in particular, NbZr(PO₄)₃ and zirconium phosphate. Therefore, the thermal expansion coefficient of the glass frit 5 can be remarkably reduced. Thus, when such refractory filler is used, the thermal expansion coefficient of the glass frit 5 can be easily controlled to 75×10⁻⁷/° C. or less. In this case, the thermal expansion coefficient of the glass frit 5 is more preferably 65×10⁻⁷/° C. or less, more preferably 55×10⁻⁷/° C. or less, particularly preferably 49×10⁻⁷/° C. or less. With this, the stress on the welding portion of the glass frit 5 becomes smaller to prevent the occurrence of stress destruction at the welding portion. Herein, the term “thermal expansion coefficient” refers to an average value of values each measured with a push-rod-type thermal expansion coefficient measurement (TMA) apparatus in the temperature range of 30 to 250° C.

Next, a process of manufacturing the OLED element package 1 configured as described above is described.

First, the glass frit 5 in a paste form is applied onto the peripheral portion of the sealing substrate 4 at a thickness of, for example, 15 μm and is then preliminarily fired so as to be temporarily cured on the sealing substrate 4.

On the other hand, on the element substrate 3, after the first electrode 6 is formed in a predetermined pattern at a thickness of, for example, 300 nm, the OLED layer 2 is formed. Then, the second electrode 7 is formed thereon in a predetermined pattern. Further, in the peripheral portion of the element substrate 3, SiO₂ films (low-refractive index layers), each having a thickness of 139 nm, and Si₃N₄ films (high-refractive index layers), each having a thickness of 100.6 nm, are alternately formed over the electrodes 6 and 7 so that the number of layers is nine in total, thereby forming the multilayer dielectric film 8. It should be noted that the multilayer dielectric film 8 is formed by alternately laminating the low-refractive index layers and the high-refractive index layers by, for example, a CVD method, a sputtering method, or a vacuum deposition method.

Thereafter, the element substrate 3 and the sealing substrate 4 are provided opposite to each other, and the glass frit 5 and the multilayer dielectric film 8 are brought into contact with each other. Then, laser light is applied from the sealing substrate 4 side to the glass frit 5 to melt the glass frit 5 so as to directly weld the glass frit 5 and the multilayer dielectric film 8. With this, the outer peripheral portions of the element substrate 3 and the sealing substrate 4 are joined over the entire periphery. As a result, the OLED layer 2 is hermetically sealed.

In addition, with the OLED element package 1 configured as described above, the following functions and effects are enjoyed.

Specifically, each of the dielectric layers constituting the multilayer dielectric film 8 can well maintain an adhesive force to the glass frit 5 as compared with a metal layer. Therefore, even without additionally providing a layer in addition to the multilayer dielectric film 8 only for the purpose of enhancing the adhesive force to the glass frit 5, the adhesive force to the glass frit 5 can be well maintained. Moreover, each of the dielectric layers constituting the multilayer dielectric film 8 does not have conductivity. Therefore, even without additionally providing another insulating layer, electric insulation from the electrodes 6 and 7 connected to the OLED layer 2 can be maintained. Thus, additionally providing an improvement layer for improving the adhesive force to the glass frit 5 or another insulating layer is not an indispensable condition. Accordingly, the degree of freedom in the design of the OLED element package 1 can be ensured.

Moreover, with the multilayer dielectric film 8 as described above, an excellent reflectance can be easily realized in the wavelength band of the laser light emitted from the laser L by selecting a material and adjusting a thickness for each of the low-refractive index dielectric layers and the high-refractive index dielectric layers. Thus, when the laser light is applied from the sealing substrate 4 side to the glass frit 5 at the time of welding of the glass frit 5, the laser light is reliably reflected at the multilayer dielectric film 8 to the glass frit 5 side so as to be effectively used to heat the glass frit 5. Therefore, the laser light transmitted through the multilayer dielectric film 8 to be applied to the electrodes 6 and 7 is reduced as much as possible. Accordingly, it is possible to reliably prevent a situation in which the electrodes 6 and 7 and the OLED layer 2 are unduly heated by the laser light to be thermally damaged.

It should be noted that the first aspect of the present invention is not limited to the embodiment described above and can be carried out in various modes. For example, although the case where the multilayer dielectric film 8 is formed directly on the electrodes 6 and 7 has been described in the above embodiment, an insulating layer may be provided therebetween. Similarly, although the case where the multilayer dielectric film 8 is welded directly to the glass frit 5 has been described, an intermediate layer may be provided between the multilayer dielectric film 8 and the glass frit 5.

Further, although the transparent electrode made of ITO and the metal electrode made of Al have been exemplified as the first electrode 6 and the second electrode 7 in the embodiment described above, other transparent electrodes made of IZO, AZO, and the like, and other metal electrodes made of Ti, Ag, Cu, Cr, Mo, and the like may also be used.

Further, although the OLED element package (OLED display device) has been described as an example in the embodiment described above, the first aspect of the present invention is similarly applicable to an electrical element package used for other devices such as an OLED lighting device or a solar cell.

Further, various types of glass frits other than the one exemplified above can be used. Specifically, for example, a glass frit containing V₂O₅-containing glass powder and β-eucryptite or zirconium phosphate tungstate or a glass frit containing Bi₂O₃-containing glass powder and cordierite or willemite may be used.

Next, an embodiment of the second aspect of the present invention is described referring to the drawings. It should be noted that, an OLED element package to be incorporated into an OLED display device is described below as an example of an electrical element package.

FIG. 3 is a longitudinal sectional view illustrating a schematic configuration of an OLED element package according to this embodiment. An OLED element package 1 comprises, as a basic configuration, an element substrate 3 on which an OLED layer 2 is formed, a sealing substrate 4 provided at a distance from a surface of the element substrate 3 on the OLED layer 2 side so as to be opposed to the element substrate 3, and a glass frit 5 for surrounding the OLED layer 2 in a frame-like fashion so as to hermetically seal a gap between the element substrate 3 and the sealing substrate 4.

Each of the element substrate 3 and the sealing substrate 4 is formed of a glass substrate having a thickness of, for example, 0.05 to 2 mm in this embodiment. It should be noted that, in some cases, a cavity having a given depth is formed on the sealing substrate 4 so as to avoid contact with the OLED layer 2 or to provide a hygroscopic material therein.

A first electrode 6 and a second electrode 7, which are respectively connected to a back side and a front side of the OLED layer 2, are provided on the element substrate 3. The electrodes 6 and 7 pass below the glass frit 5 to be guided from the OLED layer 2 to the exterior of the OLED element package 1 so as to supply electric power to the OLED layer 2. It should be noted that the electrodes 6 and 7 branch according to a predetermined pattern, as illustrated in FIG. 4. Further, the first electrode 6 on the back surface side of the OLED layer 2 is formed of, for example, a transparent electrode film (ITO film), whereas the second electrode 7 on the front surface side of the OLED layer 2 is formed of, for example, a metal electrode film such as aluminum. It should be noted that the first electrode 6 and the second electrode 7 may both be formed of a transparent electrode film.

Then, as illustrated in FIGS. 3 and 4, laser light emitted from a laser L is applied from the sealing substrate 4 side to the glass frit 5 to heat the glass frit 5 so that the glass frit softens and flows to weld the element substrate 3 and the sealing substrate 4. With this, a hermetically-sealed structure of the OLED element package 1 is formed. It should be noted that, as the laser L, for example, a near-infrared semiconductor laser (having a wavelength of 800 to 1100 nm) is used.

If the electrodes 6 and 7 are heated at the time of the laser welding of the glass frit 5, there is a possibility of thermally damaging the electrodes 6 and 7. Moreover, there is another possibility of transmitting the heat through the electrodes 6 and 7 to the OLED layer 2 to thermally damage the OLED layer 2. Therefore, in this embodiment, a metal oxide film 9 functioning as a protective film is provided between the glass frit 5 and each of the electrodes 6 and 7 so as to protect the electrodes 6 and 7 from laser light.

The metal oxide film 9 functioning as the protective layer is preferably excellent in adhesiveness to the glass frit 5 and the electrodes 6 and 7 and exhibits insulating property. As a material thereof, SiO₂, ZrO₂, Y₂O₃, TiO₂, Al₂O₃, Ta₂O₅, and Nb₂O₅ can be given.

The thickness of the metal oxide film 9 is preferably to 500 nm, 10 to 300 nm, particularly preferably 30 to 300 nm. If the thickness of the metal oxide film 9 is less than 5 nm, the effect of protecting the electrodes 6 and 7 is lowered. On the other hand, when the thickness is more than 500 nm, the amount of a stress due to a difference in thermal expansion between the glass frit 5 and the metal oxide film 9 becomes large. As a result, separation is liable to occur between the glass frit 5 and the metal oxide film 9 after the laser welding. Moreover, the thickness becomes a factor of increasing the manufacturing cost of the electrical element package.

The glass frit 5 is suitable to contain 80 to 99.95 mass % of inorganic powder comprising SnO-containing glass powder and 0.05 to 20 mass % of pigment. In this case, the content of the inorganic powder is preferably 90 to 99.95 mass %, 95 to 99.95 mass %, particularly preferably 99 to 99.95 mass %. If the content of the inorganic powder is small, the glass frit 5 does not soften and flow sufficiently at the time of laser welding, and becomes difficult to increase a welding strength. On the other hand, when the content of the inorganic powder is more than 99.95 mass %, the content of the pigment becomes relatively small, and hence the laser-light absorption performance of the glass frit 5 is lowered.

Moreover, when the content of the pigment is controlled to 0.05 mass % or more, the glass frit becomes more likely to absorb the laser light, and hence the efficiency of laser welding is improved to easily prevent the electrodes and the electrical element from being thermally damaged. On the other hand, when the content of the pigment is restricted to 20 mass % or less, it becomes easy to prevent a situation in which the glass frit devitrifies at the time of laser welding.

Preferred aspects of the average particle diameter D₅₀, the maximum particle diameter D_(max), and the glass composition of the SnO-containing glass powder are the same as those described above, and therefore the detailed description thereof is omitted for convenience.

It is preferred to set the softening point of the SnO-containing glass powder to the same as the softening point described above.

The pigment is preferably an inorganic pigment, more preferably is one kind or two or more kinds selected from carbon, Co₃O₄, CuO, Cr₂O₃, Fe₂O₃, MnO₂, SnO, Ti_(n)O_(2n-1) (n represents an integer), particularly preferably carbon. As the carbon, amorphous carbon and graphite are preferred. These pigments are excellent in chromogenic property and have satisfactory laser-light absorption performance. It is preferred to set the average particle diameter D₅₀ of the pigment and the average particle diameter D₅₀ of the primary particles of the pigment to the same values as those described above. In addition, from an environmental point of view, the pigment is preferably substantially free of a Cr-based oxide.

The glass frit 5 preferably further comprises a refractory filler. With this, the thermal expansion coefficient of the glass frit 5 can be lowered, while the mechanical strength of the glass frit 5 can be enhanced. A mixing ratio of the SnO-containing glass powder to the refractory filler in the inorganic powder is preferably adjusted to the same as that described above.

Preferred aspects of the material and the maximum particle diameter D_(max) of the refractory filler are the same as those described above.

A preferred range of the thermal expansion coefficient of the glass frit 5 is the same as that described above.

The glass frit 5 and a vehicle are preferably kneaded and processed into a paste material to be used. With this, application workability and the like can be enhanced. It should be noted that the vehicle usually contains a resin binder and a solvent. The same resin binder and solvent as those described above are preferred, and the detailed description thereof is omitted for convenience.

Separation of the binder from the paste is preferably carried out in an inert atmosphere, particularly in an N₂ atmosphere. With this, it becomes easy to prevent a situation in which the SnO-containing glass powder deteriorates at the time of separation.

Further, the paste is preferably subjected to laser welding in an inert atmosphere, particularly in an N₂ atmosphere. With this, it becomes easy to prevent a situation in which the SnO-containing glass powder deteriorates at the time of laser welding.

Next, a process of manufacturing the OLED element package 1 is described.

First, the glass frit 5 in a paste form is applied to the peripheral portion of the sealing substrate 4 at a thickness of about 40 μm and a width of about 0.6 mm by, for example, a screen printer, and is then dried and fired to decompose and volatilize a resin component and a solvent component in the paste. Thereafter, the glass frit is caused to soften and flow so as to firmly adhere to the sealing substrate 4. A thickness of the glass frit 5 after being fired is, for example, about 15 μm. In order to enhance the precision of the laser welding, a surface of the glass frit after being fired is required to be smoothed. Specifically, it is preferred to set surface roughness, the Ra value and the RMS value to 0.7 μm or less and, to 1 μm or less, respectively.

On the other hand, on the element substrate 3, after the first electrode 6 is formed in a predetermined pattern at a thickness of, for example, 150 nm, the SiO₂ film 9 is formed at a thickness of, for example, 100 nm on a region to be opposed to the peripheral portion of the sealing substrate 4 where the glass frit 5 has been printed and fired. It should be noted that the SiO₂ film 9 is formed by, for example, a CVD method, a sputtering method, or a vacuum deposition method. Thereafter, the OLED layer 2 is formed. Then, the second electrode 7 is formed thereon in a predetermined pattern.

Subsequently, the element substrate 3 and the sealing substrate 4 are provided so as to be opposed to each other so that the glass frit 5 and the SiO₂ film 9 are brought into contact with each other. Then, laser light is applied from the sealing substrate 4 side to the glass frit 5 so that the glass frit 5 is melted to soften and flow to directly weld the glass frit 5 and the SiO₂ film 9. With this, the outer peripheral portions of the element substrate 3 and the sealing substrate 4 are joined over the entire periphery. As a result, the OLED layer 2 is hermetically sealed.

It should be noted that the second aspect of the present invention is not limited to the embodiment described above and can be carried out in various modes. For example, although the case where the SiO₂ film 9 is formed directly on the first electrode 6 has been described in the embodiment described above, the film may be provided on the glass frit 5 on the sealing substrate 4 side.

Further, although the transparent electrode made of ITO and the metal electrode made of Al have been exemplified as the first electrode 6 and the second electrode 7 in the embodiment described above, other transparent electrodes made of IZO, AZO, FTO, ZnO, and the like, and other metal electrodes made of Ti, Ag, Cu, Cr, Mo, multilayer films thereof, and the like may also be used.

Further, although the OLED element package (OLED display device) has been described as an example in the embodiment described above, the second aspect of the present invention is similarly applicable to an electrical element package used for other devices such as an OLED lighting device or a solar cell.

Further, various types of glass frits other than the one exemplified above can be used. Specifically, for example, a glass frit containing V₂O₅-containing glass powder and β-eucryptite or a glass frit containing Bi₂O₃-containing glass powder and cordierite or willemite may be used.

Example 1

First, the first aspect of the present invention is described in detail based on examples. It should be noted that the first aspect of the present invention is not limited to the following examples. The following examples are mere exemplifications.

(Simulation of Frequency Characteristic of Reflectance)

Design values of film configurations of examples (No. 2 to No. 4) of the multilayer dielectric film used for the electrical element package according to the first aspect of the present invention are shown in Table 1. It should be noted that, in Table 1, a single-layer dielectric film is shown as a comparative example (No. 1).

TABLE 1 No. 1 No. 2 No. 3 No. 4 No. 5 First layer Si₃N₄ Si₃N₄ Si₃N₄ Si₃N₄ Si₃N₄ (Thickness (nm)) (100.6) (100.6) (100.6) (100.6) (100.6) Second layer — SiO₂ SiO₂ SiO₂ SiO₂ (Thickness (nm)) (139.0) (139.0) (139.0) (139.0) Third layer — Si₃N₄ Si₃N₄ Si₃N₄ Si₃N₄ (Thickness (nm)) (100.6) (100.6) (100.6) (100.6) Fourth layer — — SiO₂ SiO₂ SiO₂ (Thickness (nm)) (139.0) (139.0) (139.0) Fifth layer — — Si₃N₄ Si₃N₄ Si₃N₄ (Thickness (nm)) (100.6) (100.6) (100.6) Sixth layer — — — SiO₂ SiO₂ (Thickness (nm)) (139.0) (139.0) Seventh layer — — — Si₃N₄ Si₃N₄ (Thickness (nm)) (100.6) (100.6) Eighth layer — — — — SiO₂ (Thickness (nm)) (139.0) Ninth layer — — — — Si₃N₄ (Thickness (nm)) (100.6) Total thickness 100.6 340.1 579.7 819.2 1058.8  (nm)

Although being based on the simulation, the multilayer dielectric films having the film configurations as shown in Table 1 exhibited wavelength characteristics of the reflectance as shown in FIG. 5. As shown in FIG. 5, as compared with the comparative example (No. 1) with single layer configuration, the wavelength characteristic of the reflectance became better as the number of layers increases. In the example (No. 5) with nine layers configuration, the maximum reflectance reached even about 90%. In addition, with the design of the examples (No. 2 to No. 5), the reflectance to infrared laser light having a wavelength of 808 nm became maximum.

Example 2

(Measured Values of Frequency Characteristic of Reflectance)

Examples of film configurations of examples (No. 6 to No. 8) of the multilayer dielectric film used for the electrical element package according to the first aspect of the present invention are shown in Table 2.

TABLE 2 No. 6 No. 7 No. 8 First layer Si₃N₄ Si₃N₄ Si₃N₄ (Thickness (nm)) (100.6) (100.6) (100.6) Second layer SiO₂ SiO₂ SiO₂ (Thickness (nm)) (139.0) (139.0) (139.0) Third layer — Si₃N₄ Si₃N₄ (Thickness (nm)) (100.6) (100.6) Fourth layer — SiO₂ SiO₂ (Thickness (nm)) (139.0) (139.0) Fifth layer — Si₃N₄ Si₃N₄ (Thickness (nm)) (100.6) (100.6) Sixth layer — SiO₂ SiO₂ (Thickness (nm)) (139.0) (139.0) Seventh layer — — Si₃N₄ (Thickness (nm)) (100.6) Eighth layer — — SiO₂ (Thickness (nm)) (139.0) Total thickness 239.6 718.8 958.4 (nm)

Frequency characteristics of the reflectance of the examples (No. 6 to No. 8) are as shown in FIG. 6. Both the example with six layers (No. 7) and the example with eight layers (No. 8) had the maximum reflectance in the vicinity of the wavelength of 808 nm, and about 70% of the maximum reflectance was realized with the example with eight layers (No. 8).

Example 3

(Temperature Measurement of Electrodes at the Time of Laser Welding)

The glass frit in a paste form was printed by screen printing at a thickness of 15 μm on the peripheral portion of the glass substrate with a dimension of 40 mm in length by 50 mm in width by 0.5 mm in thickness. Thereafter, preliminary firing was performed at 500° C. for one hour to temporarily cure the glass frit, thereby manufacturing the sealing substrate.

In this case, the glass frit containing 99 mass % of the inorganic powder and 1 mass % of the pigment was used. The inorganic powder contained in the glass frit comprises 60 vol % of SnO-based glass powder and 40 vol % of the refractory filler. The SnO-based glass powder contains, as a glass composition in terms of mol %, 59% of SnO, 20% of P₂O₅, 5% of ZnO, 15% of B₂O₃, and 1% of Al₂O₃. Further, the glass powder has an average particle diameter D₅₀ of 2.5 μm and a maximum particle diameter D_(max) of 7 μm. The refractory filler is made of zirconium phosphate powder, and has an average particle diameter D₅₀ of 2 μm and a maximum particle diameter D_(max) of 8 μm. On the other hand, the pigment contained in the glass frit is made of carbon powder, and has an average particle diameter D₅₀ of 0.5 μm and a maximum particle diameter D_(max) of 3 μm.

On the other hand, the first electrode made of ITO was formed and patterned at a thickness of 150 nm on the glass substrate with a dimension of 40 mm in length by 50 mm in width by 0.5 mm in thickness. Thereafter, the OLED layer and the second electrode made of Al were formed on the glass substrate by the vacuum deposition method to manufacture the element substrate.

Thereafter, in a state in which the element substrate and the sealing substrate were provided so as to be opposed to each other under a nitrogen atmosphere, laser light having a wavelength of 808 nm was applied from the sealing substrate side to weld the glass frit to perform hermetic sealing. It should be noted that the laser light was applied at an output of 20 W on the peripheral portion of the glass substrate while being moved at 5 mm/s.

Then, temperatures of the first electrode and the second electrode at the time of laser welding were measured by a radiation thermometer. The temperature measurement at the time of laser welding was first carried out for the first electrode made of ITO. Specifically, the temperature measurement was carried out for:

(1) as a comparative example, the first electrode on which the multilayer dielectric film was not provided (No. 9);

(2) as an example, the first electrode on which the multilayer dielectric film with two layers in the same configuration as that of the above-mentioned example (No. 6) was provided (No. 10); and

(3) as an example, the first electrode on which the multilayer dielectric film with eight layers in the same configuration as that of the above-mentioned example (No. 8) was provided (No. 11). The results are shown in FIG. 7.

As can be seen from FIG. 7, the temperature of the first electrode (ITO) of the comparative example (No. 9) without the multilayer dielectric film exceeded 400° C., whereas the temperatures of the first electrodes of the examples (No. 10 and No. 11) on which the multilayer dielectric films are respectively provided were below 400° C. In particular, in the case of the example (No. 11) using the multilayer dielectric film with eight layers, the temperature of the second electrode dropped to about 220° C. Therefore, a sufficient effect of preventing the first electrode from being thermally damaged can be recognized.

Next, the temperature measurement at the time of laser welding was carried out for the second electrode made of Al. Specifically, the temperature measurement was carried out for:

(1) as a comparative example, the second electrode on which the multilayer dielectric film was not provided (No. 12);

(2) as an example, the second electrode on which the multilayer dielectric film with two layers in the same configuration as that of the above-mentioned example (No. 6) was provided (No. 13);

(3) as an example, the second electrode on which the multilayer dielectric film with six layers in the same configuration as that of the above-mentioned example (No. 7) was provided (No. 14); and

(4) as an example, the second electrode on which the multilayer dielectric film with eight layers in the same configuration as that of the above-mentioned example (No. 8) was provided (No. 15). The results are shown in FIG. 8.

As can be seen from FIG. 8, the temperature of the second electrode (Al) of the comparative example (No. 12) without the multilayer dielectric film rises to about 700° C., whereas the temperatures of the second electrodes of the examples (Nos. 13 to 15) on which the multilayer dielectric films were respectively provided were below the above temperature. In particular, in the cases of the example (No. 14) using the multilayer dielectric film with six layers and the example (No. 15) using the multilayer dielectric film with eight layers, the temperature of the second electrode dropped to about 150° C. Therefore, a sufficient effect of preventing the second electrode from being thermally damaged can be recognized.

Example 4

(Presence or Absence of Thermal Damage of Electrodes at the Time of Laser Welding)

At the time of laser welding, laser light at an output of 12 W was applied on the peripheral portion of the glass substrate while being moved at 3 mm/s to melt the glass frit. The presence or absence of thermal damage of an electrode at this time was inspected. Specifically, ITO was used as a material of the electrode, and the inspection on the electrode was carried out for:

(1) as a comparative example, the electrode on which the multilayer dielectric film was not provided (No. 16);

(2) as an example, the electrode on which the multilayer dielectric film with two layers in the same configuration as that of the above-mentioned example (No. 6) was provided (No. 17); and

(3) as an example, the electrode on which the multilayer dielectric film with eight layers in the same configuration as that of the above-mentioned example (No. 8) was provided (No. 18). It should be noted that whether or not the electrode was thermally damaged was determined based on the presence or absence of conduction. Specifically, in the case where the electrode maintains a conductive state, it is determined that thermal damage is “absent”. In the case where the electrode is in a non-conductive state, it is determined that thermal damage is “present”. This is because, if the electrode is thermally damaged, the conductive path is disconnected. The results are shown in Table 3.

TABLE 3 No. 16 No. 17 No. 18 Presence or absence of thermal damage Present Absent Absent

Further, along with the inspection, temperatures of the frit glass at the time of laser welding were inspected. The results are shown in FIG. 9.

As shown in FIG. 9, as compared with a comparative example without the multilayer dielectric film on the electrode (No. 16), in the examples (Nos. 17 and 18) in which the multilayer dielectric films were respectively provided on the electrodes, the temperatures of the frit glass became high. Even based on such the results, it can be recognized that the laser light was reflected by the multilayer dielectric film to the frit glass side so that the laser light is effectively used to heat the frit glass in the examples (Nos. 17 and 18).

Example 5

Hereinafter, the second aspect of the present invention is described in detail based on examples. It should be noted that the following examples are mere exemplifications. The second aspect of the present invention is not limited to the following examples.

Table 4 shows examples (Sample Nos. 1 to 4) and a comparative example (Sample No. 5) of the second aspect of the present invention.

TABLE 4 Comparative Examples Example No. 1 No. 2 No. 3 No. 4 No. 5 Protective film SiO₂ SiO₂ SiO₂ SiO₂ None Thickness (nm) 50 100  300  1000  Laser-light Glass frit 730  750  740  750  740 irradiation average temperature (° C.) conditions A Resistance Before 80 80 80 80  80 Output: 22 W value irradiation Speed: 25 mm/s (Ω · cm) After 90 80 80 80 No conduction Beam diameter: irradiation φ0.8 mm HAST test ∘ ∘ ∘ x ∘ Laser-light Glass frit 640  630  640  630  640 irradiation average temperature (° C.) conditions B Resistance Before 80 80 80 80  80 Output: 15 W value irradiation Speed: 10 mm/s (Ω · cm) After 80 80 80 80 120 Beam diameter: irradiation φ0.8 mm HAST test ∘ ∘ ∘ x ∘ Laser-light Glass frit 680  690  685  680  690 irradiation average temperature (° C.) conditions C Resistance Before 80 80 80 80  80 Output: 12 W value irradiation Speed: 3 mm/s (Ω · cm) After 85 85 80 80 No conduction Beam diameter: irradiation φ0.8 mm HAST test ∘ ∘ ∘ x ∘

First, the glass frit and a vehicle were kneaded so that a viscosity became about 150 Pa·s (25° C. and a shear rate of 4), and then further kneaded with a three-roll mill to obtain a paste thereof.

Herein, the glass frit containing 99.75 mass % of the inorganic powder and 0.25 mass % of the pigment was used. The inorganic powder in the glass frit contained 60 vol % of SnO-based glass powder and 40 vol % of the refractory filler. And the SnO-based glass powder contained, as a glass composition in terms of mol %, 59% of SnO, 20% of P₂O₅, 5% of ZnO, 15% of B₂O₃, and 1% of Al₂O₃. Further, the glass powder had an average particle diameter D₅₀ of 2 μm and a maximum particle diameter D_(max) of 5 μm. The refractory filler was made of zirconium phosphate powder, and had an average particle diameter D₅₀ of 1.5 μm and a maximum particle diameter D_(max) of 3.5 μm. The pigment contained in the glass frit was made of carbon powder, and had an average particle diameter D₅₀ of primary particles of about 30 nm. A polyethylene carbonate resin (MW: 129000) was used as a resin component of the vehicle, whereas propylene carbonate was used as a solvent component. It should be noted that a softening point of the glass frit was 400° C., and a thermal expansion coefficient of the glass frit was 49×10⁻⁷/° C. (measurement temperature range of 30 to 300° C.). Herein, the softening point was a value measured with a DTA apparatus, whereas the thermal expansion coefficient was a value measured with a TMA apparatus.

Next, the glass frit in a paste form prepared as described above was printed by screen printing on the peripheral portion of a glass substrate (OA-10G manufactured by Nippon Electric Glass Co., Ltd.) with a dimension of 40 mm in length by 50 mm in width by 0.5 mm in thickness so that the glass frit had a thickness of about 30 μm and a width of about 0.6 mm, followed by drying under the conditions of 120° C. for 30 minutes under an air atmosphere. After that, the resultant was fired under the conditions of 480° C. for 10 minutes under a nitrogen atmosphere to decompose and volatilize a resin component in the paste and to cause the glass frit to firmly adhere to the glass substrate, thereby preparing a sealing substrate. A thickness of the glass frit after being fired was about 16 μm. Surface roughness of the glass frit after being fired was measured. The Ra value was 0.5 μm, and the RMS value was 0.8 μm.

On the other hand, the first electrode made of ITO was formed and pattered at a thickness of 150 nm on a glass substrate (OA-10G manufactured by Nippon Electric Glass Co., Ltd.) with a dimension of 50 mm in length by 50 mm in width by 0.5 mm in thickness. Thereafter, the SiO₂ film was formed at a thickness of 50 nm, 100 nm, 300 nm, or 1000 nm in the region where the glass frit was to adhere. The SiO₂ film was formed at a width of about 1 mm so as to prevent the glass frit and the ITO film from coming in contact with each other. It should be noted that the oxide film was not formed for Sample No. 5. Thereafter, the OLED layer and the second electrode made of Al were formed on the glass substrate by the vacuum deposition method to form the element substrate.

Subsequently, in a state in which the sealing substrate and the element substrate were provided so as to be opposed to each other under the nitrogen atmosphere, laser light having a wavelength of 808 nm was applied from the sealing substrate side along the glass frit to weld the sealing substrate and the element substrate. It should be noted that the laser-light irradiation conditions were as described in the table.

Sample Nos. 1 to 5 were evaluated as follows.

The temperature of the glass frit at the time of irradiation with laser light was measured by using the radiation thermometer.

The electric resistance of the ITO film located immediately below the glass frit was measured before and after the irradiation with laser light so as to evaluate whether or not the ITO film thermally deteriorated.

After a HAST test (highly accelerated temperature and humidity stress test) was conducted for the glass frit which had been subject to the laser welding, whether or not the separation of the glass frit was observed. The glass frit without separation was evaluated with Symbol “o”, whereas the glass frit for which the separation occurred was evaluated with Symbol “x”. It should be noted that the HAST test was conducted under the conditions of 121° C., 100% RH, and 2 atm for 24 hours.

As is apparent from Table 4, no great change was observed in the resistance value of the ITO film for Sample Nos. 1 to 4, between before and after the irradiation of laser light. This fact shows that the SiO₂ film was able to properly protect the ITO film to prevent the ITO film from thermally deteriorating due to the irradiation of laser light. In particular, no unfavorable situation such as separation was observed in Sample Nos. 1 to 3 after the HAST test. This fact shows that the glass frit and the SiO₂ film firmly adhered to each other.

On the other hand, in sample No. 5 without the SiO₂ film, the resistance value of the ITO film increased after the irradiation of laser light. In particular, under the laser-light irradiation conditions A and C, the ITO film was thermally damaged to a severe extent, and therefore it was impossible to measure the resistance value of the ITO film.

REFERENCE SIGNS LIST

-   -   1 OLED element package     -   2 OLED layer     -   3 element substrate     -   4 sealing substrate     -   5 glass frit     -   6 first electrode     -   7 second electrode     -   8 multilayer dielectric film     -   9 metal oxide film (SiO₂ film)     -   L laser 

1. An electrical element package, comprising: an element substrate on which an electrical element is provided; a sealing substrate provided at a distance from a surface of the element substrate on a side of the electrical element so as to be opposed to the element substrate; and a glass frit for hermetically sealing a gap between the element substrate and the sealing substrate so as to surround the electrical element, wherein the electrical element package comprises a protective film for protecting an electrode from laser light applied in welding the glass frit, the protective film being provided between the element substrate and the glass frit.
 2. An electrical element package, comprising: an element substrate on which an electrical element is provided; a sealing substrate provided at a distance from a surface of the element substrate on a side of the electrical element so as to be opposed to the element substrate; and a glass frit for hermetically sealing a gap between the element substrate and the sealing substrate so as to surround the electrical element, wherein: the electrical element package comprises a reflective film for reflecting laser light applied in welding the glass frit, the reflective film being provided between the element substrate and the glass frit; and the reflective film is formed of a multilayer dielectric film obtained by alternately laminating a low-refractive index dielectric layer and a high-refractive index dielectric layer.
 3. The electrical element package according to claim 2, wherein the multilayer dielectric film is welded directly to the glass frit.
 4. The electrical element package according to claim 2, wherein the multilayer dielectric film is formed directly on an electrode connected to the electrical element.
 5. The electrical element package according to claim 2, wherein the low-refractive index dielectric layer has a refractive index of 1.6 or less, and the high-refractive index dielectric layer has a refractive index of 1.7 or more.
 6. The electrical element package according to claim 2, wherein the multilayer dielectric film has a reflectance of 50% or more to the laser light.
 7. The electrical element package according to claim 2, wherein the glass frit contains 80 to 99.7 mass % of inorganic powder comprising SnO-containing glass powder and 0.3 to 20 mass % of a pigment.
 8. The electrical element package according to claim 7, wherein the SnO-containing glass powder contains, as a glass composition in terms of mol %, 35 to 70% of SnO and 10 to 30% of P₂O₅.
 9. An electrical element package, comprising: an element substrate on which an electrical element is provided; a sealing substrate provided at a distance from a surface of the element substrate on a side of the electrical element so as to be opposed to the element substrate; and a glass frit for hermetically sealing a gap between the element substrate and the sealing substrate so as to surround the electrical element, wherein the electrical element package comprises a metal oxide film for protecting an electrode from laser light applied in welding the glass frit, the film being provided between the element substrate and the glass frit.
 10. The electrical element package according to claim 9, wherein the metal oxide film has a thickness of 10 to 500 nm.
 11. The electrical element package according to claim 9, wherein the metal oxide film comprises any one of SiO₂, ZrO₂, Y₂O₃, TiO₂, Al₂O₃, Ta₂O₅, and Nb₂O₅.
 12. The electrical element package according to claim 9, wherein the metal oxide film is welded directly to the glass frit.
 13. The electrical element package according to claim 9, wherein the metal oxide film is formed directly on an electrode connected to the electrical element.
 14. The electrical element package according to claim 9, wherein the glass frit contains 80 to 99.5 mass % of inorganic powder comprising SnO-containing glass powder and 0.05 to 20 mass % of a pigment.
 15. The electrical element package according to claim 14, wherein the SnO-containing glass powder contains, as a glass composition in terms of mol %, 35 to 70% of SnO and 10 to 30% of P₂O₅. 